The flame arrester inserts of these flame arrester arrangements are predominantly produced in a winding process using thin stainless steel strips. Here, a smooth metal strip is wound up together with a uniformly corrugated metal strip and the two thus form turns of a preferably disc-like arrangement. The passage gaps result from the corrugated metal strip resting on the two adjacent smooth metal strips, so that defined passage gaps are produced. Depending on the flammability of the gas, the passage gaps, given a predefined axial length, must not exceed a predefined cross-sectional surface area. In order to ensure an adequate flow velocity for easily flammable gases, it may therefore be necessary to wind up the flame arrester inserts with a large cross-sectional surface area, that is to say to produce them with a large winding radius. The turns are preferably arranged such that they lie on one another spirally, but also, in the form of closed circular turns, can each comprise a smooth metal strip and a corrugated metal strip.
It has been found that, given a predefined maximum cross section of the passage gaps, it is expedient to implement the gap length required for the cooling of the gas not with a single flame arrester insert but with a plurality of flame arrester inserts, that is to say at least two, it being advantageous to arrange an intermediate layer between the flame arrester inserts, which permits a radial distribution of the gas flow emerging from the one flame arrester insert and entering the adjacent downstream flame arrester insert.
If the flame arrester inserts are laid directly on one another without an intermediate layer, on the other hand, the passage gaps are not aligned with one another accurately, so that the flame arrester inserts lying on one another form resultant channels of which the effective passage gaps are reduced in size in an undefined way as compared with the passage gaps of a flame arrester insert, since the free cross-sectional surface area of the assembly of flame arrester inserts lying on one another is reduced. As a result, the pressure loss during the flow through is increased sharply. The intermediate layers provided in the flame arrester arrangement of the generic type thus serve as spacer elements, which prevent a reduction in the free cross-sectional surface area of the flame arrester inserts lying one behind another. In a conventional design, the housing of the flame arrester arrangement forms an enclosing cage having a closed shell wall. Since the gas can expand in the radial direction between the flame arrester inserts, care must be taken that the gaps produced between the edge of the flame arrester inserts and the inner wall of the enclosing cage are smaller than the gaps in the flame arrester inserts themselves. Otherwise, there would be a diversionary path around the flame arrester insert, on which the gas is not cooled in the manner provided by the respective flame arrester insert, so that a flashback through the flame arrester arrangement possibly occurs, which means that a catastrophe can be triggered if, for example, an explosion progresses into a gas storage tank which is intended to be protected by the flame arrester arrangement.
In particular during the production of large flame arrester inserts, which can have diameters up to 2 m, it is problematic in fabrication terms to avoid the occurrence of relatively large gaps between the flame arrester insert and the surrounding housing. Such large flame arrester inserts cannot usually be produced to be exactly round. It is therefore known to wind such a flame arrester insert directly in the enclosing cage and, at the points at which relatively large gaps form, then to assemble in smooth filter strip, in order in this way to produce reliable edge contact between the flame arrester insert and the enclosing cage. However, this has the disadvantage that the flame arrester insert is fitted so firmly in the enclosing cage that it cannot be removed in practice for cleaning and renewal purposes, in particular when large amounts of contamination or even corrosion occur/s between the filter and the enclosing cage.
In order to be able to remove a flame arrester insert simply for servicing purposes, a gap that is as large as possible between the flame arrester insert and the enclosing cage is expedient. However, it is necessary to prevent the flame from the gas flow from flowing around one or more flame arrester inserts via the radially outer gap and thus rendering the flame arrester useless.
If at most two flame arrester inserts are used, radially outer supporting rings can bear directly axially on the outside of the flame arrester inserts, so that a radially outer flow around the latter by the gas running through the flame arrester arrangement is not possible. In the case of more than two flame arrester inserts, it is known to use an enclosing cage having stepped walls, in which each flame arrester insert bears in a sealing manner on the metal of the enclosing cage. Such an enclosing cage is very expensive to produce and cannot be mass-produced, since different models and diameters are necessary, depending on the number of flame arrester elements. Furthermore, in order to be suitable for different gases, the flame arrester inserts have to be produced in different sizes.